speak vs articulate

speak is not an adjective while articulate is an adjective.

Word	Noun	Adjective	Verb	Adverb
speak	No	No	Yes	No
articulate	No	Yes	Yes	No

speak (adjective)	articulate (adjective)
	expressing yourself easily or characterized by clear expressive language
	consisting of segments held together by joints

speak (verb)	articulate (verb)
express in speech	speak, pronounce, or utter in a certain way
exchange thoughts; talk with	express or state clearly
use language	put into words or an expression
give a speech to	provide with a joint
make a characteristic or natural sound	unite by forming a joint or joints